The invention relates to a method for testing cigarette heads, at least one region of a cigarette head being irradiated with light, and light reflected by the cigarette head being received by a detector in such a way that irradiating and received reflected light run at an angle to one another, the irradiated region is imaged on the detector and a signal generated by the detector is evaluated. The invention also relates to an apparatus for testing cigarette heads, having a light source and an optical system for producing at least one region, irradiated with light, on a cigarette head, and having a detector, for receiving light reflected by the cigarette head, which is arranged in such a way that irradiating and received reflected light run at an angle to one another and the irradiated region can be imaged on the detector.
A test method or a testing apparatus is known for contactless testing of cigarette heads, in the case of which a straight line is radiated onto a tobacco-end cigarette head. If the cigarette is not properly filled with tobacco, the line no longer appears as a straight linexe2x80x94if it is observed from a different viewing anglexe2x80x94, but as a wavy line or as a broken wavy line. This image is detected by a sensor. Finally, the image points which lie inside and outside a narrow region around an imaginary, theoretical straight line are counted and their ratio is formed. If this ratio exceeds a limiting value, this is formed to indicate that a cigarette is not properly filled.
This type of testing has the disadvantage that it is inaccurate and does not permit exact statements on the state of a cigarette. The invention is therefore based on the problem of improving the testing of cigarettes and permitting more accurate statements on the state of a cigarette.
For the purpose of solving this problem, the method according to the invention is characterized in that, when evaluating, a possible deviation, in particular a distance, of the position of the image of the irradiated region from an expected position of an image of a corresponding region of an ideal cigarette head on the detector is determined, the deviation being used to determine the distance of the irradiated region from a desired position of this region. Furthermore, the problem is solved by an apparatus according to the invention which is characterized by an evaluation device which evaluates a signal generated by the detector in order to determine a possible deviation, in particular a distance, in the position of the image of the irradiated region from an expected position of an image of a corresponding region of an ideal cigarette head, in order to determine from the deviation the distance of the irradiated region from a desired position of this region.
A cigarette head can be measured in a contactless fashion by means of the invention. In this case, it is preferred for the light beam of a laser or another bright light source to be used and focused onto a cigarette head via a lens. One or more image points are thereby illuminated essentially at the test distance. A lens focuses the reflected light on a position-sensitive detector. If the illuminated region is not located in its desired position, this leads to a deviation in the image point on the position-sensitive detector, or to a deviation in the image of the illuminated region with reference to an expected position of the image on the detector. On the basis of the geometrical arrangement of the cigarette head or the desired position of the cigarette head, the direction of incidence of the light and direction of the reflected light, as well as of the distances of these positions from the lens or from the optical system and from the detector, this deviation, which may be expressed as a distance, yields the distance of the irradiated region in relation to a desired position of this region.
The invention achieves a very high measuring accuracy. Furthermore, an instantaneous exposure of the cigarette head suffices for determining these distances. Consequently, a cigarette head can be measured as it moves and in a contactless fashion. This permits a high operating speed of the cigarette packaging or cigarette producing machine.
It is preferred to irradiate and evaluate a plurality of regions of a cigarette head. It is possible in this way to judge the correct construction, in particular of recess filter or Russian cigarettes and, in particular, to measure the length of a hollow section of a tip sleeve of such cigarettes. Furthermore, the correct, in particular round construction of such tip sleeves can be monitored by irradiating a plurality of points or relatively small regions onto the end region of a tip sleeve.